Hi,
In my fMRI paradigm, I have 4 conditions (1~4, and conditions 3 and 4 are the main EVs of interest) and 1 time slot of baseline of doing nothing.
Model 1:
I model the 4 conditions separately. To get activations of the main EV of interest, the contrast is (0 0 1 0) for condirion 3 and (0 0 0 1) for 4.
Model 2:
I model 1 and 2 conditions together as 1 EV (because they are both EV of no interest) and conditions 3 and 4 separately. To get activations of the main EV of interest, the contrast is (0 1 0) for condirion 3 and (0 0 1) for 4.
I found the activations of both models are very identical, but it seems that activation in model 2 is slightly larger (and with slightly higher statistics) than that in model 2.
Which model should I use!?
Thanks.
Mark
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